Roll gap control



y 5, 1970 A. M. LLOYD 3,509,815

ROLL GAP CONTROL Filed Aug. 28, 1967 ROLLS SAME L ROLLS Y. n van-b r *omcys United States Patent 3,509,815 ROLL GAP CONTROL Anthony MichaelLloyd, Walkington, near Beverley, England, assignor to Rose, Downs &Thompson Limited, Kingston-upon-Hull, Yorkshire, England Filed Aug. 28,1967, Ser. No. 663,631 Claims priority, application Great Britain, Aug.31, 1966, 38,873/ 66 Int. Cl. B30b /14 6 Claims ABSTRACT OF THEDISCLOSURE A control mechanism for maintaining a constant roll gapbetween rolls for treating vegetable materials. The mechanism providesnon-contact sensing means located adjacent the roll gap and responsiveto changes in the distances between the sensing means and the barrels ofthe two adjacent rolls. The sensing means controls a mechanism foradjusting the roll gap, so as to maintain that gap at a constant value.The sensing means are preferably pneumatic, air jets being directedtowards the two roll barrels and the back pressure being dependent onthe proximity of the barrels from the sensing means.

This invention relates to rolls. The invention is particularlyapplicable to flaking rolls for operating on organic material where itis necessary to control the gap between the rolls to a tight toleranceand where the actual roll gap is small.

In conventional roll gap control arrangements the sensing means arenormally displaced from the roll barrels themselves and measure someother parameter such as the distance between the chocks or the rollnecks, for force exerted on the rolls, or the state of the outgoingmaterial. While these other parameters will to some degree be a functionof the roll gap and allow some control, they will not be an accuratemeasure of the roll gap or take into account all the factors on whichthe gap is dependent.

Accordingly the present invention provides a pair of rolls havingadjustment means for adjusting the roll gap therebetween, sensing meansarranged to detect a change in the distance between the sensing meansand the roll barrels, and control means responsive to the sensing meansto control the adjustment means to maintain the roll gap at a presetvalue.

Preferably, a separate adjustment means, sensing means and control meansis associated with each end of the rolls.

In one form the adjustment means are wedges arranged between the chocksof the rolls, the chocks being prestressed against the wedges.

Preferably the sensing means comprise jets of air from nozzles placed inclose proximity to the roll barrel surfaces so that a variation in gapbetween the roll barrels produces a variation in gap between the rollbarrels and the nozzles and hence a variation in the back pressure inthe airline. This change in back pressure may be used both to centralisethe air nozzles assembly and to control the adjustment means.

By directly sensing the change in position of the surface of the rollbarrels, inaccuracies arising in previously proposed control systems arereduced. The system according to the invention will thus automaticallycorrect for alterations in roll gap due to roll expansion andcontraction with temperature, non-uniform flow of feed across the lengthof the rolls, and uneven wear of rolls across the length of the rolls.

One embodiment of roll gap control system, in ac- 3,509,815 Patented May5, 1970 ice cordance with the invention, will now be described, by wayof example only, with reference to the accompanying diagrammaticdrawing.

In the drawing a pair of co-operating flaking rolls 12, have roll barrelsurfaces 13, and roll necks 14 rotatably supported in bearings 15 inbearing chocks 16. Drive means for rotating the rolls in the directionof the arrows are not shown. One bearing chock engages one end 17 of ahousing while the other bearing chocks engages a piston 18 slidable in acylinder 19 mounted in the other end 20 of the housing. Pressurisedhydraulic fluid is supplied from a pump 21 to the cylinder to prestressthe chocks against a roll gap adjusting device 22 comprising a pair ofoppositely sloping wedge members 23, 24, the wedge surfaces of whichengage corresponding wedge surfaces on the chocks, the wedge membersbeing mounted on oppositely threaded portions of a screw 25 rotatable bya hydraulic motor 26 driven through a hydraulic control valve 27 by thepump 21.

For convenience the roll barrels are shown twice in the drawing but itshould be realised that they are in fact the same rolls.

A sensing device in the form of an air nozzle assembly 28 supplied withair on line 29 is mounted so that its two air nozzles 30 are adjacentthe surfaces of the two roll barrels respectively at the ends thereof,the axes of the nozzles making an obtuse angle with one another so thatthey are substantially aligned with two coplanar symmetrical radii ofsaid roll barrels. The nozzles are mounted on a self centering controlvalve 31 so that the back pressure from the nozzles maintains theassembly equidistant from the rolls, and thus the pressure in the twonozzles the same. The nozzles are thus symmetrical about the planethrough the roll gap and normal to the plane containing the axes of therolls. The nozzles are also connected on line 32 to a diaphragm 33 whichis in turn connected to the hydraulic control valve 27. In operation anychange in the back pressure in the nozzles acts through the diaphragmand hydraulic control valve to adjust the wedge position to restore theroll gap X to its preset value. The assembly 28 may be adjustablymounted on a screw or the like for movement towards or away from therolls for initially setting the roll gap.

It should be understood that an exactly similar but intillependentsystem is provided at the other ends of the TO S.

Capacitance or other types of proximity transducers could be used inplace of the pneumatic system, and other types of roll gap adjustmentcould equally well be used, for example by controlling the prestressingload.

While the system is particularly useful for flaking rolls operating onorganic material, it can also be used on similar applications fornon-organic materials or where the magnitude of the roll gap and thetolerance on the roll gap are large.

What is claimed is:

1. The combination of a pair of co-acting rolls for treating vegetablematerials and having adjustment means for adjusting the roll gap betweensaid rolls,

non-contact sensing means arranged adjacent said roll gap tocontinuously detect changes in the distances between said sensing meansand the barrels of said rolls, and control means controlled by saidsensing means and controlling said adjustment means to maintain saidroll gap at a preset value.

2. The combination according to claim 1 in which said adjustment meansand said sensing means are arranged at one end of the roll barrels andwhich additionally comprises further and similar adjustment means andsensing means arranged at the other end of said roll barrels and furthercontrol means similarly controlled by said further sensing means andcontrolling said further adjustment means.

3. The combination according to claim 1 in which said adjustment meanscomprise Wedges located between checks for said rolls and means forurging said chocks into engagement with said wedges.

4. The combination according to claim 1 in which said sensing means ispneumatic and comprises a pair of nozzles at an angle to one another anddirected respectively at the adjacent said roll barrels, a change insaid roll gap producing a change in the dynamic back pressure and saidcontrol means being responsive to said pressure.

5. The combination according to claim 4 in which said control meansincludes a pressure sensitive diaphragm connected to said pneumaticsensing means to be responsive to said back pressure, and controllingsaid adjustment means.

6. The combination according to claim 1 in which said sensing means isadjustably mounted so that it will automatically maintain itselfequidistant from the two roll barrels.

References Cited UNITED STATES PATENTS 895,005 8/1908 Delbert -168 X1,365,521 1/1921 McNeil 100168 X 2,025,562 12/1935 Balsiger 100-169 X2,051,434 8/1936 Cavagnaro 100-168 2,075,574 3/1937 Dahlstrom 72-2l2,344,274 3/1944 Stacom 100-47 2,455,285 11/ 1948 Versaw.

2,424,856 7/1947 Schmuck 100169 X 3,186,200 6/ 1965 Maxwell. 3,358,48512/1967 De Caro et al. 72-21 WALTER A. SCHEEL, Primary Examiner L. G.MACHLIN, Assistant Examiner US. Cl. X.R. 24137

